Compare unit prices
Put the jars, packs and bottles side by side, in whatever units their labels use, and see which gives you the most for your money.
Best value first
- 1
Large jar
£3.50per kgBest value
- 2
Twin pack
£3.53per kg0.8% dearer
- 3
Imported jar
£4.96per kg41.7% dearer
Large jar gives the most for your money. The dearest costs 41.7% more per unit than the cheapest.
How the ranking works
Each item's price is divided by everything in it (packs × size), converted to grams, millilitres or items, so a 1 lb jar and a 340 g pot can sit side by side. The lowest unit price comes first, and every other item shows how much more you pay per unit:
% dearer = (item's unit price ÷ cheapest unit price − 1) × 100
In the example, the 1 kg jar at £3.50 is £3.50 per kg, the twin pack of 340 g jars at £2.40 is £3.53 per kg (0.8% dearer) and the 16 oz import at £2.25 is £4.96 per kg (42% dearer). A gap of a few percent is often worth ignoring if the smaller pack suits you better.
Tips
- Set "Show prices per" to the unit on the shelf labels you are checking.
- Names are optional; unnamed rows are numbered.
- Weights, volumes and counts can't be mixed in one list.
Sources
- NIST, Guide to the SI, Appendix B.9: conversion factors between metric, US and imperial units.
Questions
Why can a dearer pack rank first?
The ranking is per unit, not per pack. A £3.50 jar holding 1 kg costs less per gram than a £2.25 jar holding 454 g, even though you hand over more at the till.
What does "% dearer" mean?
How much more you pay per gram, millilitre or item than for the best-value product. 25% dearer means every 100 g costs a quarter more than it does in the cheapest pack.
How many items can I compare?
Up to twelve at once. Rows with a missing price or size are left out of the ranking until you fill them in.
Is my list saved?
Yes, on this device only: it is kept in your browser's local storage so you can finish it in the shop, and never uploaded. Clear empties the list.